1. Field of the Invention
This invention relates to the production of granules, more particularly surfactant-containing granules, which may be used in laundry detergents, dishwashing detergents or cleaning products.
2. Discussion of Related Art
The production of highly concentrated surfactant granules is known, for example, from earlier International patent application WO 93/04162, according to which the surfactant granules are produced by granulation in a fluidized bed. To this end, a surfactant preparation containing a non-surface-active liquid component is granulated and, at the same time, dried, if desired with incorporation of an inorganic or organic solid. The surfactant preparation may contain surfactants or surfactant mixtures from the group of anionic, nonionic, amphoteric and cationic surfactants, preferably anionic surfactants, more particularly fatty alkyl sulfates, C.sub.9-13 alkyl benzene sulfonates and sulfofatty acid methyl esters, and/or nonionic surfactants, more particularly liquid ethoxylated fatty alcohols containing 2 to 8 ethylene oxide groups per mole of alcohol.
Earlier German patent application P 42 32 874.8 describes a corresponding fluidized-bed granulation process in which anionic surfactant granules are obtained by neutralization of anionic surfactants in their acid form, the process being characterized in that the anionic surfactants in their acid form are neutralized and, at the same time, granulated with a powder-form neutralizing agent and, if desired, the granules formed are simultaneously dried. In this process, too, it is possible to use either an anionic surfactant in its acid form on its own or a surfactant mixture from the group of anionic surfactants in their acid form in combination with anionic, nonionic, amphoteric and/or cationic surfactants, more particularly anionic surfactants and/or liquid ethoxylated fatty alcohols containing 2 to 8 ethylene oxide groups per mole of alcohol.
The processes mentioned above give highly concentrated surfactant granules of preferably high apparent density. However, problems in regard to the flow properties or rather the tackiness of the granules can arise in the processing of low-melting and poorly crystallizing anionic surfactants, for example alkyl benzene sulfonates and .alpha.-sulfofatty acid methyl esters, and where relatively large quantities of liquid nonionic surfactants are used.
DD 228 458 A1 and DD 251 044 A3 describe a process for the production of surfactant-containing granules in a fluidized bed, in which the granules formed are powdered with a solid in the fluidized bed in order to reduce their tackiness and hence to reduce their tendency to form lumps on leaving the fluidized bed. The disadvantage of this solution is that considerable proportions of the solid used are incorporated within the granules before they leave the fluidized bed and, accordingly, are unable to contribute towards the outer coating of the granules. In addition, this process is confined to the addition of solid, powder-form granule stabilizers.
The problem addressed by the present invention was to provide a process for the production of granules in a fluidized bed, the granules being coated with a stabilizer which may be solid or even liquid to paste-like in the processing state. Another problem addressed by the invention was to protect the granules against outside influences, for example chemical influences.